<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <script>
        let num1= +prompt('请输入第一个数字')
        let num2= +prompt('请输入第二个数字')
        let num3= prompt('请输入符号')
        switch (num3) {
            case '+':
            alert(`两个数的加法操作是${num1+num2}`)
            break
            case '-':
            alert(num1-num2)
            break
            case '*':
            alert(num1*num2)
            break
            case '/':
            alert(num1/num2)
            break
            default:
            alert('输入错误')
        }
    </script>
</body>
</html>